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This invention relates in general to the design of headphones and, in particular, to headphones that have an inner flexible headband or a headstrap coming in contact with the user""s head, and this headstrap may alter in length or size to ensure proper fit of an earpiece to the head. The headstrap is anchored at each end to an outer headband, interconnecting a pair of earpieces, and also providing a resilient inner force to hold the headphone in place. Secondly, this invention relates to the headphones having particular cup structure designed to fit the earpiece over the user""s ear.
There are numerous headphones having the mentioned above structure varying in acoustical parameters, design specifics and so forth. Nevertheless, it is rather hard to find an inexpensive headphone which can be worn comfortably for a relatively long period of time in one session. This is especially true for young computer users who spend long hours in front of the computer screen playing games or surfing the Net for their favorite musical and video files. A headphone""s ability to adjust completely and comfortably to a particular user is becoming as important as its acoustical parameters.
The problem of a headphone adjustment mainly consists of two components that can be classified by a particular function which has to be performed to have comfortable and sustained accommodation to the user. Firstly, a headphone""s headband has to provide proper positioning of the earpiece in a vertical axial direction in order to accommodate the distance from the scalp to the ear which varies from user to user. It constitutes the axial adjustment problem. Secondly, the headphone""s driver unit has to fit closely and comfortably to the outer part of the ear, the pinna, in order to create an ergonomically and acoustically necessary coupling space between them. This is a problem of adjustment to the pinna.
There are two commonly used ways to to adjust a headphone in a vertical axial direction. The first is when an earpiece and a headband are movably connected, providing telescopically adjustable positioning to the earpiece. This is telescopic detent-based adjustment. The second is when the vertical adjustment is based on changing the geometry of a headstrap having some elastic members, without manually moving parts, thus providing a headphone with axial self-adjustment.
Telescopic Detent-Based Adjustment
In the first case, the telescopically connected earpiece is moved manually, and its holding in place is made possible by means of a special positioning member, a detent, releaseably engaging one of corresponding depressions or openings. The detent can be part of either a headband or an earpiece. Consequently, the earpiece assembly, as well as the headband, can include a plurality of depressions or openings being designed to accommodate the detent. There are several headphone designs based on this concept. The design with the plurality of openings and the wedge shaped detent is described in U.S. Pat. No. 4,189,788 to Schenke et al. (1980). The elastic projecting member at the headband""s end is shown in U.S. Pat. No. 4,445,457 to Jingu Akira (1984). The headphone with progressively shallow depressions is disclosed in U.S. Pat. No. 5,117,465 to James T. MacDonald (1992).
The main disadvantage of this design concept is a certain contradiction inherent to it. The detent""s holding power has to be substantial enough to secure the earpiece in place, and, at the same time, it becomes a source of inconvenience when one needs to move the earpiece in order to adjust it. The greater is the holding power of the detentxe2x80x94the more resistance it creates to adjust the earpiece. Moreover, a headphone detent""s ability to function greatly depends on its material properties. The wide application of plastic with significantly less resilience and durability, than that of stainless steel, results in lesser holding power, which can be applied by the detent. It means that during use the earpiece support becomes liable to get loose or shift from the headband, causing dislocation of the earpiece from the proper position on the pinna.
Therefore an optimal axial adjustment mechanism that balances the ease of use with precise and sustainable accommodation to the wearer is rather difficult to achieve in a framework of the telescopic detent-based adjustment. Alternatively, a concept of axial self-adjustment has been employed to satisfy users needs for a quick and comfortable fit of the headphones.
Axial Self-Adjustment
The conventional way of vertical axial self-adjustment is based on the use of some structural resilience in various embodiments. The most common way is when a headstrap is connected to earpieces by means of an elastic suspension in the form of elastic members, such as helical springs, flat coil springs or bands. Initially this idea was embodied in a headphone design described in U.S. Pat. No. 3,919,501 to Cech et al. (1975). A rather sophisticated suspension concept is realized in the form of a wind-in mechanism which is disclosed in U.S. Pat. No. 5,406,037 to Nageno et al (1995). The idea of having a suspender member consisting of some expendable and non-expendable sections is realized in U.S. Pat. No. 5,574,795 to Seki (1996).
Despite the differences the basic self-adjustment concept requires that the elastic member suspends the earpieces in such a manner that they are retracted upwardly by the resilient force of this elastic member and must be extended downward manually from their retracted position during the application to a wearer""s ears. During the downward movement elastic member is stretched and it produces a return force corresponding to the respective distance between the top of the user""s head and the ear opening. This return force pulls earpieces upward, and in order to hold them in place it must be counteracted by the friction between the earpiece pad and the ear. The friction is directly proportional to the opposite horizontal forces pressing the earpieces against the user""s ears. These forces are produced by the headband""s resilient resistance to its being pulled apart as a result of adjustment to the head.
Apparently, in order to have a headphone comfortably fitting the user, all these forces affecting the wearer""s head must be balanced. The more elastic member is stretchedxe2x80x94the greater friction has to be applied to balance the return forces created by this action. Thus, the disadvantage of this concept is that the system inevitably creates excessive pressure on the scull and ears, and especially, if the wearer""s head is bigger than the average one. Additionally, the typical problem of these adjustment mechanisms based on the material""s elasticity is that after some period of usage some of them are beginning to slacken off, causing dislocation of the earpiece from the proper position on the pinna. The common way to avoid this is to increase the stiffness of the elastic member, consequently making the initial pressure even greater. Considering the nature of these balanced forces and the great variety of human forms and shapes the necessary equilibrium can be reached either for a limited number of people or for a limited time only.
Therefore this type of adjustment provides quick but eventually uncomfortable and unsustainable accommodation to the user, and thus it is best suited for a situation when a headphone has to be shared by a group of users. For instance, headphones in musical records stores are generally used by different people for a relatively short period of time. To the contrary, in regards to personal usage, the most typical situation is when a headphone is used for a relatively long period of time by one person, and that requires to have comfortable, precise and sustainable accommodation to the user.
The apparent diversity of ear shapes creates a problem of an earpiece""s proper adjustment in order to provide close and comfortable fit to the pinna. The earpiece""s close fit allows to form an acoustically desirable coupling space between a driver and the auditory canal of the user""s ear.
The common way is to combine adjustment in a horizontal plane by using a C-shape arm holding the earpiece, and adjustment in a vertical plane by having a hinge connecting the headband and the bracket. This structure is designed on the assumption that a sculpturally complex three-dimensional shape, like the human ear, can be significantly simplified without losing its essential properties. It can be accepted as a basic design model if a headphone is used for a relatively short working session, but for prolonged usage it becomes a source of the user""s discomfort.
The more advanced approach allows to perceive the human shapes as complex as they really are. In regards to the ear it means allowing for the earpiece to have some relative angular motion in different directions in order to accommodate the driver unit in relation to the user""s pinna. There are some headphones where a driver unit is attached to a headband by a means of a ball-and-socket joint providing certain angular motion.
For instance, this way of attachment allowing biaxial motion of a face plate carrying a transducer is described in U.S. Pat. No. 4,965,836 to Andre et al. (1990). A small ball integrally formed on the hub of the spider element belonging to the face plate, is fitted into a socket, provided by a socket plate, which is permanently attached to the inside surface of the cover. The certain disadvantage of this joint is its bulky and complex supporting structure. Accordingly, it necessitates to have additional room to accommodate the joint, and this significantly increases the headphone""s overall size. Secondly, after some period of usage and consequent mechanical wear, this type of joint can unexpectedly fall apart, because its design only relies on material properties and the joint is not secured in any other way.
An alternative way to accommodate a conventional ball-and-socket joint is employed in the HD 475 Expression Line headphone manufactured by Sennheiser Electronic GmbH and Co. KG, Am Labor, Germany. This headphone sports a joint placed in a special recessed area of the driver housing 12. Its way of adjustment is shown in FIGS. 1 through 2B. The small spherical knob 13 belongs to the driver unit 12, and the mating socket 11, consisting of two longitudinally placed ribs, is part of the headband 10. The unwanted ramification of the joint""s recessed positioning is that it negatively affects the acoustical quality of the driver housing 12. When a speaker driver is activated, it vibrates and pushes air forward, producing sound. At the same time sound waves are transmitted backward bouncing off the recessed area and other housing""s walls differently, thus producing standing waves and other forms of sound diffraction.
Thereafter, the disadvantages of the adjustment in current systems of headphones can be summarized according to the functions which they perform:
(a) The telescopic detent-based adjustment is a conceptually contradictory system. The detent""s holding power has to be strong enough to secure the earpiece in place, and, at the same time, it becomes a nuisance when one needs to move the earpiece in order to adjust it. The greater is the holding power of the detentxe2x80x94the more resistance it creates to adjust the earpiece.
(b) With the introduction of plastic as a main structural material the earpiece detent-based support becomes liable to get loose or shift from the headband, causing dislocation of the earpiece from the proper position on the pinna, thus making the adjustment unsustainable.
(c) Considering the nature of forces which are involved in the self-adjustment process and the great variety of human forms, the axial self-adjustment system inevitably creates excessive pressure on the scull and ears, and especially, if the wearer""s head is bigger than the average one. Therefore this type of adjustment provides quick but eventually unsustainable and uncomfortable accommodation to the user. The accommodation is unsustainable because the system""s elastic member gets loose due to its continuous usage, and it is uncomfortable because of gradually increasing impact of excessive pressure over the time of wearing.
(d) The ball-and-socket joint based on the xe2x80x9cspherical knob at the end of a shaftxe2x80x9d concept is rather bulky and often needs a complex supporting structure. Accordingly, it necessitates having additional room to accommodate the joint, and this significantly increases the headphone""s overall size.
(e) In some embodiments the joint can be positioned in a special recessed area of the driver cup in order to reduce its size. The side effect of this design is that it compromises the acoustical quality of the cup. Sound waves bounce off the recessed area parallel walls and other cup""s walls in a different way, thus generating standing waves as well as other forms of sound diffraction.
(f) After some period of usage and consequent mechanical wear, this type of joint could unexpectedly fall apart, because its design only relies on material properties and the joint is not secured in any other manner.
Accordingly, it is an object of this invention to provide a headphone device which avoids the above-mentioned disadvantages of the prior art, and to match the needs of various wearers by its complete and comfortable adjustment to them. More specifically, it is an object of the present invention to provide a headphone device capable of quick, precise and sustainable axial adjustment in a wide range of motion without causing uncomfortable pressure on the user""s scull or ears. Another object of the present invention is to create an ergonomically correct and acoustically desirable interface between the ear and the headphone.
This innovative headphone design has evolved from the observation of a conventional self-adjusting headset quite often not fitting comfortably and creating excessive pressure either on the scull or ears. These problems preclude the user from wearing it comfortably for a relatively long time in a single session. Also, the apparent diversity of human shapes, sculls, and ears in particular, is much greater than it was originally assumed as the basis for development of the conventional self-adjustable headset. This has to be taken into account by enabling earpieces to have substantial angular motion in all directions, and thus allowing to align the earpieces with any kind of user""s pinna.
These problems are solved in the proposed headphone by creating two innovative systems of adjustment, headpiece vertical axial adjustment and earpiece self-adjustment, and then incorporating them into the proposed headset. Therefore, several objects and advantages of the present invention are:
(a) The headphone axial adjustment, being essentially an accommodation to the head""s parameters, has a wide range of motion and provides means for the user to choose and then keep the most comfortable earpiece position in relation to the size and shape of his or her head. A sliding block-gear rack mechanism provides substantial holding power to secure the earpiece in place, and, at the same time, it allows to reduce it to a necessary minimum when the user moves the earpiece in order to adjust it.
(b) All structural elements, including detents, of the sliding block-gear rack mechanismxe2x80x94are inexpensive injection molded plastic. Its innovative design allows to hold a chosen position of the earpiece for any period of time without being loose or dislocated.
(c) The proposed axial adjustment mechanism does not produce vertical return forces with corresponding excessive pressure on the head that any conventional self-adjustment mechanism generates. It allows to reduce the pressure created by the headband to a minimally necessary level only for balancing the headphone weight and to hold earpieces in an acoustically proper position, thus providing precise and sustainable adjustment of the headpiece to the user.
(d) The earpieces self-adjustment is provided by the innovative hollow ball-and-socket joint design. It incorporates the spherical driver housing, driver cup, and the headband arm as main structural elements of the joint. It does not require any additional space to accommodate the joint.
(e) With the present invention the driver cup""s geometry is defined by acoustical requirements as well as structural ones. The acoustically optimal spherical driver cup does not produce standing waves and other distortions of sound. Also, the range of motion is substantially greater than that of a conventional ball-and-socket joint based on the xe2x80x9cspherical knob at the end of a shaftxe2x80x9d design.
(f) The proposed hollow ball-and-socket joint can endure prolonged usage because its all structural elements are securely hold together by sandwiching the driver cup between the arm and the holder.
With this invention a wearer adjusts the headphone by a simple downward move of the earpieces while simultaneously depressing the release buttons with either the index or middle finger, making it easy to use. When a comfortable position of the earpieces is reached, the release buttons are set free thus allowing for locking the earpieces directly in that location. Further manipulation is unnecessary, because the earpieces are completely self-adjustable in respect to the user""s ears.
The synergetic combination of the axial degree of freedom in vertical adjustment with the three rotational degrees of freedom in the ball-and-socket joint allows to create an ergonomically and acoustically necessary coupling space between the user""s ear and the headphone without causing uncomfortable pressure either on the scull or the ear. It radically differs from the commonly used methods by giving the user a means to control the process of adjustment while keeping this process as quick and simple as that of a conventional self-adjustable headset. Therefore, the proposed adjustment system balances the ease of use with comfortable, precise and sustainable accommodation to the user. Further objects and advantages of the invention will become apparent from a consideration of the drawings and ensuing description.